1. Field of the Invention
The invention relates to a continuous method for treating a textile surface made of differentially dyeable nylon yarns with a stainblocker composition to impart stain resistance thereto, and to the article produced thereby.
2. Description of the Prior Art
In the current floor covering market there is a perceived need for carpets made from differentially dyeable nylon yarns. By the term “differentially dyeable” it is meant that the article contains yarns having at least two different dyeabilities, such as acid dyeable yarn and cationic (“cat”) dyeable yarn. Often a desired aesthetic effect in a carpet is possible only by combining yarns of these two different dyeabilities. Both dyeabilities are available in various dye depths, such as light, regular, deep and extra deep acid dye and light and regular cat dye.
In the current floor covering market there is a perceived need for carpets made from for a differentially dyeable carpet to exhibit a high degree of stain resistance. Compositions referred to as “stainblockers” are commonly applied to non-differentially dyeable carpets or carpet tiles to impart stain resistance. There is presently available both a continuous process and a discontinuous, or batch-wise, process for applying a stainblocker composition to a carpet made of non-differentially dyeable yarns.
Continuous Conventional Process. The steps of a conventional process for applying a stainblocker composition to a textile surface made of non-differentially dyeable yarns are listed along the left hand side in FIG. 3. In the conventional continuous process a running line of colored carpet (colored as by dyeing or printing), after rinsing and suction hydroextraction, is passed through an aqueous liquid treatment bath containing a stainblocker composition and a surfactant. The temperature of the bath is in the range from twenty to sixty degrees Celcius (20 to 60° C.). The residence time of the carpet in the bath is usually not adjusted as an independent critical parameter but is instead a function of the speed of the carpet line. After removal from the bath the carpet passes through a steam chamber wherein it is exposed to saturated steam for about sixty to ninety (60 to 90) seconds. Thereafter, conventional finishing steps for the carpet typically include: a suction hydroextraction operation where residual liquid is vacuumed from the carpet; a cold water rinse operation (either by spraying or passing the carpet through a dip trough); another suction hydroextraction operation; and a final drying.
Batch-wise Conventional Process. The batch-wise process for applying the stainblocker composition and a surfactant to a textile surface made of non-differentially dyeable yarns (such as a broadloom carpet) is termed the “winch/beck” process. In the batch-wise winch/beck process discrete dyed carpets are immersed in a vat a stainblocker composition and a surfactant. The temperature of the bath in the batch-wise winch/beck process is slightly higher than in the continuous process, in the range from seventy to seventy-five degrees Celcius (70 to 75° C.), and the residence time in the bath is on the order of twenty minutes. After removal from the bath, the carpet is subjected to the conventional finishing steps such as rinsing with cold water in situ, or after unloading from the hot application bath, rinsed by spray bar followed by a vacuum extraction operation to ensure no residual stainblocker is left.
In both the continuous process and the batch-wise process the stainblocker composition is preferably of the anionic functionalized type, and more preferably, of the sulphone resole type having nonionic functionality. It should be noted that in FIG. 3 the anionic functionalized type stainblocker compositions are referred to as “Stainblocker A”, while the sulphone resole type stainblocker compositions are referred to as “Stainblocker B”.
Tile Production To produce carpet tiles treated with a stainblocker composition it is common practice first to treat a broadloom carpet with a stainblocker composition in one of the manners specified, and after a backing is applied, to cut the broadloom carpet into pieces of the desired size to form carpet tiles.
Stainblockers Suitable anionic functionalized type stainblocker compositions include sulphonated phenol formaldehyde condensate types, maleic acid anhydride types, acrylate dispersions and mixtures thereof. Anionic functionalized type stainblocker compositions should be present between three weight percent (3 wt %) and five weight percent (5 wt. %) based on the weight of the nylon carpet fiber. When anionic functionalized type stainblocker compositions are used, the pH of the bath must be adjusted to between 2 and 5.
Examples of commercially available anionic functionalized type stainblocker compositions are available from E. I. Du Pont de Nemours and Company, Wilmington, Del., under the trademarks SR 300, SR 400 and SR 500; from Du Pont de Nemours International S. A., Geneva, Switzerland, under the trademark NRD 334; from Allied Colloids, Bradford/West Yorkshire, U.K., under the trademark Alguard RD; and from Bayer AG, Leverkusen, Germany, under the trademark Baygard DT.
When sulphone resole type stainblocker compositions with nonionic functionality are used, they should be present at between four weight percent (4 wt. %) and six weight percent (6 wt. %) based on the weight of the nylon carpet fiber, and the pH must be adjusted to between 6 and 7.5. An example of a commercially available sulphone resole type stainblocker composition with nonionic functionality is available from E. I. Du Pont de Nemours and Company, Wilmington, Del. under the trademark Zelan 8236.
The pH of the treatment bath may be adjusted by known acid donor additives such as acetic acid, citric acid and sulfamic acid.
Surfactants A surfactant may be added to the stainblocker bath separately or may be included as part of the stainblocker composition. The surfactant may be anionic, amphoteric or nonionic in nature. Preferably, the surfactant used will be either an alkylated diphenyl oxide disulfonate sodium salt, alone or in combination with an alkylnaphtalene sulfonic acid formaldehyde condensate sodium salt. The surfactant is generally added to the bath at a rate of between one (1) and four (4) grams per liter. Suitable surfactants are available from E. I. Du Pont de Nemours and Company, Wilmington, Del. under the trademark Zelan 50; from Dow Chemical Company, Midland, Mich., under the trademark Dowfax 3B2; or from BASF AG, Ludwigshafen, Germany, under the trademark Primasol NF.
Problem With Conventional Methods for Differentially Dyeable Textile Surfaces. Unfortunately, when either the continuous process or the batch-wise process is used to apply a stainblocker composition to a broadloom carpet containing differentially dyeable yarns the cationic dyestuff “bleeds” from the cat dyeable yarn into the surrounding stainblocker treatment bath, resulting in an unacceptable visual color change.
Low Liquor Method. The only publicly known system to apply a stainblocker composition to a differentially dyeable carpet is a method known as the “low liquor” method. Using the “low liquor” method a differentially dyeable carpet may attain at least a modest degree of stain resistance. In the “low liquor” method a cold-foamed liquor including a stainblocker composition and a fluorocarbon material are co-applied topically to the carpet. Thereafter the carpet is dried, without steam or water rinse. In the past, the stainblocker composition typically utilized was the acrylate dispersion sold by 3M Corporation under the trademark “FX-661”, while the fluorocarbon material typically utilized was those sold by 3M Corporation under the trademarks “FC-3611”, “FC-3602” or “FC-1395”. However, the low liquor method is useful only with a carpet having a very low “wet pick-up”, on the order of fifteen to twenty percent (15-20%). Wet pick-up (wpu) is the ratio of the weight of the liquid picked-up by the carpet from a treatment bath to the weight of the carpet. Moreover, with the low liquor method, the stainblocker composition penetrates into only about the upper twenty-five percent (25%) of the height of the pile elements of a differentially dyeable carpet. This depth of stainblocker penetration is not believed to be sufficient to impart a high degree of stain resistance.
Accordingly, in view of the foregoing, it is believed advantageous to provide a process for treating an article having a textile surface containing differentially dyeable nylon yarns, such as a broadloom carpet or carpet tiles, to impart a high degree of stain resistance thereto, while maintaining good color stability.